The present invention relates to gas lasers, and more particularly to a hypersonic gas laser which converts kinetic energy to vibrationally excited energy.
The most closely related lasing device is the so called gasdynamic laser as described by Dr. Edward T. Gerry in the Society of Photo Optical Instrumentation Engineers Journal, volume 9, pp 6170, January 1971. In a gasdynamic laser, lasing action is produced by a very rapid expansion of a hot gas mixture through supersonic (Mach numbers 1-5) nozzles. The CO.sub.2 gasdynamic laser uses the rapid expansion to "freeze" vibrational energies in nitrogen molecules which subsequently get transferred to the upper lasing vibratory level of CO.sub.2 molecules. This produces the inversion necessary for lasing action since the vibratory energy of the lower lasing CO.sub.2 levels do not "freeze" during the rapid expansion, but is relaxed or depopulated to the level appropriate to local thermodynamic conditions.
The dynamics of this rapid expansion process puts very extreme design requirements on such devices. They require a large number of supersonic nozzles with very small throat widths which:
1. produce wakes in the laser cavity, PA1 2. require very precise alignment, PA1 3. limit their operating lifetime and/or lasing duration due to severe heat transfer characteristics, and PA1 4. must be built to very close design tolerance with the attendant expense.
Besides the nozzle engineering requirement, the "quick freeze" concept limits the gas mixture to very small water percentages so that the water, besides depopulating the lower lasing levels during the expansion process (which is its function) does not also depopulate the upper lasing level of the CO.sub.2 molecules. This has the result that combustion driven devices cannot use air and common hydrocarbon fuels, but rather must use mixtures of poisonous and noxious gases such as carbon monoxide, nitrous oxide, cyanogen, etc. the efficiency of the gasdynamic laser is on the order of 1.5%.